"28 inch" was (and still is) a standard wheel size for adult bikes in my part of the world, and has the same 622mm diameter as 700C (except for 28 x 1 1/2, which is 635, but much less common).

I dug out the wheels I mentioned earlier. The rims are unmarked, except for the rather neat blue label around the valve stem that says "Weinmann" and "700C". They came off an early sixties high end supersport bike, so I'd expect them to be of good quality. The rim profile looks similar but not quite the same, I think. No eyelets either.

The Dunlop valves were also standard on anything but racing bikes (or those pretending to be). Those had "French valves", of course.